package com.cloudhopper.commons.util.windowing;


import java.lang.ref.WeakReference;
import java.util.List;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import com.cloudhopper.commons.util.UnwrappedWeakReference;


/**
 * 窗口监控工具类，并触发事件给监听器
 */
public class WindowMonitor<K,R,P> implements Runnable {
    private static final Logger logger = LoggerFactory.getLogger(Window.class);
    
    private final WeakReference<Window<K,R,P>> windowRef;
    private final String monitorThreadName;

    public WindowMonitor(Window<K,R,P> window, String monitorThreadName) {
        this.windowRef = new WeakReference<Window<K,R,P>>(window);
        this.monitorThreadName = monitorThreadName;
    }

    @Override
    public void run() {
        String currentThreadName = null;
        try {
            if (this.monitorThreadName != null) {
                currentThreadName = Thread.currentThread().getName();
                Thread.currentThread().setName(monitorThreadName);
            }
            Window<K,R,P> window = windowRef.get();

            // check if the window using this monitor was GC'ed
            if (window == null) {
                logger.error("The parent Window was garbage collected in this WindowMonitor(): missing call to Window.reset() to stop this monitoring thread (will throw exception to cancel this recurring execution!)");
                throw new IllegalStateException("Parent Window was garbage collected (missing call to Window.reset() somewhere in code)");
            }

            if (logger.isTraceEnabled())
                logger.trace("Monitor running... (current window.size [" + window.getSize() + "])");

            List<WindowFuture<K,R,P>> expired = window.cancelAllExpired();
            if (expired != null && expired.size() > 0) {
                if (logger.isTraceEnabled())
                    logger.trace("Monitor found [" + expired.size() + "] requests expired");
                // process each expired request and pass up the chain to handlers
                for (WindowFuture<K,R,P> future : expired) {
                    for (UnwrappedWeakReference<WindowListener<K,R,P>> listenerRef : window.getListeners()) {
                        WindowListener<K,R,P> listener = listenerRef.get();
                        if (listener == null) {
                            // remove this reference from our array (no good anymore)
                            window.removeListener(listener);
                        } else {
                            try {
                                listener.expired(future);
                            } catch (Throwable t) {
                                logger.error("Ignoring uncaught exception thrown in listener: ", t);
                            }
                        }
                    }
                }
            }
        } finally {
            if (currentThreadName != null) {
                // change the name of the thread back
                Thread.currentThread().setName(currentThreadName);
            }
        }
    }
}
